My daughter highlighted her way through AP Literature and AP US History, working assiduously evening after evening for months at a time. She got 4s in both examinations too suggesting that her study habits were excellent. Obviously, that wasn’t the only thing she did but it was certainly a major component.

What is interesting is that she struggled in her first year of university and self-determined that, actually, her study habits were pretty poor. With that in mind, I have been examining various ways of studying that she had to see whether her teachers understood what had high and what had low utility. One of those techniques that her teachers did not discourage was highlighting. Daniel Willingham and a number of colleagues carried out a research study including a literature search to discover effective learning techniques that students might use. They said about highlighting that “The techniques typically appeal to students because they are simple to use, do not entail training, and do not require students to invest much time beyond what is already required for reading the material”.

But highlighting is not a high return learning technique for the following reasons:

  1. The cognitive phenomenon known as the “isolation effect” shows that students might do well or better on material that is highlighted but then do worse on material that is not highlighted
  2. Students highlight idiosyncratically – some students highlight almost everything and this has two outcomes. Because everything is highlighted, there is no differentiation of information and so memory is not engaged. At the same time the act of highlighting everything reduces the processing required than to differentiate also degrading memory.
  3. Students highlight idiosyncratically – some students highlight very little. Interestingly, a couple of studies showed that only being allowed to highlight one sentence per paragraph resulted in performance higher than indiscriminate or no highlighting.

The reality is that most studies have shown no benefits from using highlighting as a learning technique. Indeed, a concerning study showed that highlighting is most useful, theoretically, for learning information but that it negatively impacts the ability to make inferences (connections across ‘facts’). As with many techniques, studies show that if the underlining is perfect – akin to the incredibly important learning technique of summary – then learning does actually make gains. But students do not do this.

So what can and should we teach to our students to learn? The following table summarizes their findings and can provide useful avenues to pursue: